Secondary batteries used as on-vehicle drive power sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs, PHEVs) or the like have been developed. In the on-vehicle drive power sources, high capacity and high output characteristics are required. A large number of batteries are connected in series or in parallel. Prismatic secondary batteries are widely used for these batteries, because of their space efficiency.
A method for welding a boundary part of a swaged joint portion with high energy beams such as laser beams is proposed as a method for realizing lower resistance in a battery terminal part or a joint part inside a battery.
JP 2010-33766 A discloses a battery including a power-generating element, a battery case storing the power-generating element, an inner conduction member, a terminal member, and a resin spacer. The inner conduction member is disposed in the battery case, is electrically connected to one electrode of the power-generating element, and includes a penetrating connection part penetrating the battery case and protruding to the outside of the battery case, The terminal member is disposed outside the battery case, is welded to the penetrating connection part of the inner conduction member, and forms a welded part melted with the penetrating connection part of the inner conduction member by welding. The resin spacer is interposed between the battery case and at least a battery case side region of the terminal member than the welded part. The penetrating connection part includes an overlapping part overlapping with an outer surface located on a side reverse to the outer surface of the terminal member opposed to the battery case. The welded part is formed in the overlapping part and the terminal member by abutting welding of the overlapping part and the terminal member using energy beams. Thereby, the inner conduction member and the terminal member can be welded while the deterioration of the resin spacer is suppressed.
However, since higher reliability is required for the secondary batteries used for the on-vehicle drive power sources or the like, further improvements in the secondary batteries are desired.
It is an object of the present invention to provide a prismatic secondary battery having further improved reliability.